Your going to need a volt meter to accurately test this. A test light is not going to do it. You have power right before the fuel pump but the light is dim so we do not know if the pump is trying to use that power and the circuit is low on amps or the circuit is low on amps prior to even getting to the pump. So far its looking like a wire thats faulty and has resistance or the pump has a poor ground. Use the diagram below if needed

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The engine does not matter, I knew what you meant since the 4.6 is the only option.

Okay check the fuse that powers the switch side of the relay before and during this same test with the inertia switch unplugged. We need to see where your losing 5 volts with nothing on the circuit even being used.

thanks for you help with this.. you were able to get us going in the right direction.. we just recently were able to find a broken wire... from the fuse to the relay.. repaired the wire and now im off and running

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